Methods for forming semiconductor devices including thermal processing

ABSTRACT

Methods for fabricating semiconductor memory devices may include forming a first conductive layer for a first electrode on a semiconductor substrate, forming a dielectric layer on the first conductive layer, and forming a second conductive layer for a second electrode on the dielectric layer. Portions of the second conductive layer and the dielectric layer can be removed, and a thermal process can be performed on the second conductive layer and the dielectric layer. The thermal process can reduce interface stress between the second conductive layer and the dielectric layer and/or cure the dielectric layer. In addition, the dielectric layer may be maintained in an amorphous state during and after the thermal process.

RELATED APPLICATIONS

The present application claims the benefit of priority as a divisionalapplication of U.S. patent application Ser. No. 10/629,430 filed Jul.29, 2003 now U.S. Pat. No. 7,172,946, which claims the benefit ofpriority from Korean Patent Application No. 2002-73820, filed on Nov.26, 2002 in the Korean Intellectual Property Office. The disclosures ofboth of the above referenced applications are incorporated herein intheir entirety by reference.

FIELD OF THE INVENTION

The present invention relates to methods for manufacturing semiconductordevices, and more particularly, to methods for manufacturing capacitors.

BACKGROUND OF THE INVENTION

As the integration of semiconductor devices has increased, the areaoccupied by individual devices on a semiconductor substrate (chip) hasbeen reduced. Information storage capacitors for DRAM devices, however,may need to maintain a same or increased capacitance within a reducedarea. Accordingly, various methods have been developed to provideincreased capacitor electrode surface areas. For example, capacitorshaving lower electrodes with three-dimensional shapes such ascylindrical shapes or fin shapes have been provided. In addition,hemispheric grains have been coated on surfaces of lower electrodes,thickness of dielectric layers have been reduced, and dielectric layershaving high dielectric constants and/or formed of ferroelectricmaterials have been provided.

When the thickness of a dielectric layer is reduced, leakage currentsmay occur due to tunneling effects. Accordingly, when a material havinghigh electric constant, such as Ta₂O₅ or BST ((Ba,Sr)TiO₃), is used as adielectric material, a polysilicon layer may be unsuitable for use as acapacitor electrode. Thus, when a material having a high dielectricconstant or a ferroelectric material is used as a dielectric layer, ametal such as platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh),or osmium (Os), having a high work function, may be used as an electrodematerial.

A method for manufacturing a conventional Metal-Insulator-Metal (MIM)capacitor will now be discussed with reference to FIGS. 1A and 1B.

Referring to FIG. 1A, a conductive layer 20 for a lower capacitorelectrode is deposited on a semiconductor substrate 10. Here, theconductive layer 20 is formed of Pt, Ru, Ir, Rh, or Os. A dielectriclayer, such as a tantalum oxide layer 30, is deposited on the conductivelayer 20. The tantalum oxide layer 30 is deposited in an amorphous stateso that the dielectric characteristics of the tantalum oxide layer 30may be relatively poor. On the other hand, when the tantalum oxide layer30 is crystallized, the dielectric constant may increase but leakagecurrent characteristics may deteriorate. Accordingly, after the tantalumoxide layer 30 is deposited, a thermal process for improving thedielectric constant can be performed at a temperature less than thatrequired to crystallize the amorphous tantalum oxide layer 30. Such acuring process can be performed at a temperature of, for example, about600° C. in a nitrogen atmosphere.

Referring to FIG. 1B, a conductive layer 40 for an upper electrode isdeposited on the cured tantalum oxide layer 30. Here, the conductivelayer 40 is formed of the same material as the conductive layer 20.Thereafter, to measure the characteristics of a capacitor, theconductive layer 40 and the tantalum oxide layer 30 are dry etched.Thus, a predetermined portion of the conductive layer 20 is exposed. Inaddition, a thermal process is performed to relieve stress at theinterface between the conductive layer 40 and the tantalum oxide layer30 due to lattice defects. Here, the thermal process for relievingstress is performed at a low temperature of, for example, about 400° C.in an oxygen atmosphere.

However, the thermal processes after depositing the dielectric layer andetching the conductive layer for the upper electrode may complicate theconventional method for manufacturing an MIM capacitor. In other words,since a wafer may need to be transferred for each thermal process, theconventional method may require an increased amount of time, andcontaminants may remain on the wafer.

SUMMARY OF THE INVENTION

According to embodiments of the present invention, methods forfabricating a semiconductor memory device may include forming a firstconductive layer for a first electrode on a semiconductor substrate,forming a dielectric layer on the first conductive layer, and forming asecond conductive layer for a second electrode on the dielectric layer.Portions of the second conductive layer and the dielectric layer can beremoved, and a thermal process can be performed on the second conductivelayer and the dielectric layer at a temperature of at least about 400°C. More particularly, the thermal process may include heating the secondconductive layer and the dielectric layer to a first temperature in therange of about 450° C. to 600° C. in an inert gas atmosphere, andheating the second conductive layer and the dielectric layer to a secondtemperature in the range of about 350° C. to 450° C. in a gas atmosphereincluding oxygen. Forming the dielectric layer can also be preceded bydepositing a seed layer on the first conductive layer, and crystallizingthe seed layer.

Performing the thermal process can include heating the dielectric layerand the second conductive layer at a temperature in the range of about450° C. to 600° C. in an inert gas atmosphere. In an alternative,performing the thermal process can include heating the dielectric layerand the second conductive layer at a first temperature in the range ofabout 350° C. to 450° C. in a gas atmosphere including oxygen, and thenheating the dielectric layer and the second conductive layer at a secondtemperature in the range of about 450° C. to 600° C. in an inert gasatmosphere. In another alternative, performing the thermal process caninclude heating the dielectric layer and the second conductive layer ata first temperature in the range of about 650° C. to 700° C. in an inertgas atmosphere, and then heating the dielectric layer and the secondconductive layer at a second temperature in the range of about 350° C.to 450° C. in a gas atmosphere including oxygen.

In yet another alternative, performing the thermal process can includeheating the dielectric layer and the second conductive layer at atemperature in the range of about 650° C. to 700° C. in an inert gasatmosphere. In still another alternative, performing the thermal processcan include heating the dielectric layer and the second conductive layerat a first temperature in the range of about 350° C. to 450° C. in a gasatmosphere including oxygen, and then heating the dielectric layer andthe second conductive layer at a second temperature in the range ofabout 650° C. to 700° C. in an inert gas atmosphere.

The first conductive layer may include at least one material selectedfrom the group consisting of platinum (Pt), ruthenium (Ru), iridium(Ir), rhodium (Rh), and/or osmium (Os), and the second conductive layermay include a same material as the first conductive layer. Moreover, thedielectric layer may include tantalum oxide, and forming the dielectriclayer may include depositing tantalum oxide at a temperature in therange of about 380° C. to 500° C. using chemical vapor deposition (CVD).In addition, removing portions of the second conductive layer and thedielectric layer may include dry etching the second conductive layer andthe dielectric layer.

Performing the thermal process may include performing the thermalprocess on the second conductive layer and the dielectric layer afterremoving portions of the second conductive layer and the dielectriclayer. Moreover, the thermal process may reduce an interface stressbetween the second conductive layer and the dielectric layer and/or curethe dielectric layer. In addition, the thermal process may be performedon the second conductive layer and the dielectric layer whilemaintaining the dielectric layer in a substantially amorphous stateduring and after the thermal process.

According to additional embodiments of the present invention, methodsfor fabricating a semiconductor memory device may include forming afirst conductive layer for a first electrode on a semiconductorsubstrate, forming a tantalum oxide layer on the first conductive layer,and forming a second conductive layer for a second electrode on thetantalum oxide layer. Portions of the second conductive layer and thetantalum oxide layer can be removed, and a thermal process may beperformed to reduce an interface stress between the second conductivelayer and the tantalum oxide layer and to cure the tantalum oxide layer.Moreover, the tantalum oxide layer can be maintained in a substantiallyamorphous state during and after the thermal process.

According to still additional embodiments of the present invention,methods for fabricating a semiconductor memory device may includeforming a first conductive layer for a first electrode on asemiconductor substrate, forming a tantalum oxide layer on the firstconductive layer, and forming a second conductive layer for a secondelectrode on the tantalum oxide layer. Portions of the second conductivelayer and the tantalum oxide layer can be removed, and a thermal processcan be performed to reduce interface stress between the secondconductive layer and the tantalum oxide layer and to crystallize thetantalum oxide layer.

According to still additional embodiments of the present invention,methods for fabricating a semiconductor memory device may includeforming a first conductive layer for a first electrode on asemiconductor substrate, forming a seed layer on the first conductivelayer, and crystallizing the seed layer. A tantalum oxide layer can beformed on the crystallized seed layer, and a second conductive layer fora second electrode can be formed on the tantalum oxide layer. Portionsof the second conductive layer and the tantalum oxide layer can beremoved, and a thermal process can be performed to reduce an interfacestress between the second conductive layer and the tantalum oxide layerand to cure the tantalum oxide layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross-sectional views illustrating a conventionalmethod for manufacturing a metal-insulator-metal (MIM) capacitor.

FIGS. 2A through 2C are cross-sectional views illustrating methods formanufacturing semiconductor memory devices according to embodiments ofthe present invention.

FIG. 3 is a graph illustrating equivalent oxide thicknesses of tantalumoxide layers according to embodiments of the present invention.

FIG. 4 is a graph illustrating leakage currents of capacitors accordingto embodiments of the present invention.

FIG. 5 is a graph illustrating leakage currents of capacitors withrespect to changes in temperature according to embodiments of thepresent invention.

FIG. 6 is a graph illustrating equivalent oxide thicknesses of tantalumoxide layers according to embodiments of the present invention.

FIG. 7 is a graph illustrating leakage currents of capacitors accordingto embodiments of the present invention.

FIGS. 8A through 8C are cross-sectional views illustrating methods formanufacturing semiconductor memory devices according to embodiments ofthe present invention.

FIG. 9 is a graph illustrating equivalent oxide thicknesses of tantalumoxide layers according to embodiments of the present invention.

FIG. 10 is a graph illustrating leakage currents of capacitors accordingto embodiments of the present invention.

DETAILED DESCRIPTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which preferred embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the concept of the invention to those skilled in the art. In thedrawings, the size and the thickness of layers and regions areexaggerated for clarity. It will also be understood that when a layer isreferred to as being on another layer or substrate, it can be directlyon the other layer or substrate, or intervening layers may also bepresent.

FIGS. 2A through 2C are cross-sectional views illustrating methods formanufacturing metal-insulator-metal (MIM) capacitors according toembodiments of the present invention. Referring to FIG. 2A, a conductivelayer 110 for a lower electrode is deposited on a semiconductorsubstrate 100. Here, the semiconductor substrate 100 may include, forexample, MOS transistors, bit lines, and/or insulating layers thatinsulate each layer. The conductive layer 110 for the lower electrodemay be formed of, for example, a metal such as platinum (Pt), ruthenium(Ru), iridium (Ir), rhodium (Rh), and/or Osmium (Os), having arelatively high work function. A tantalum oxide layer (Ta₂O₅) 120 can bedeposited on the conductive layer 110 for the lower electrode to providea capacitor dielectric layer. Here, the tantalum oxide layer 120 can beformed using chemical vapor deposition (CVD) at a temperature in therange of about 380° C. to 500° C. Thereafter, a conductive layer 130 foran upper electrode can be deposited on the tantalum oxide layer 120. Theconductive layer 130 for an upper electrode can be formed of the samematerial as the conductive layer 110 for the lower electrode. A curingof the tantalum oxide layer 120 can be omitted prior to forming theconductive layer 130.

Referring to FIG. 2B, the conductive layer 130 for the upper electrodeand the tantalum oxide layer 120 can be dry etched to expose portions ofthe conductive layer 110 for the lower electrode. Accordingly, sidewallsof the conductive layer 130 for the upper electrode and the tantalumoxide layer 120 can be exposed. Referring to FIG. 2C, a thermal processcan be performed on the resultant structure to relieve an interfacestress between the conductive layer 130 for the upper electrode and thetantalum oxide layer 120, and to improve the dielectric constant of thetantalum oxide layer 120.

The thermal process can be performed by various methods as discussedbelow. In a first example of thermal processing, a first thermal processcan be performed on the resultant structure at a temperature in therange of about 450° C. to 600° C. and in an inert gas atmosphere forabout 30 minutes. Thereafter, a second thermal process can be performedon the resultant structure at a temperature in the range of about 350°C. to 450° C. in a gas atmosphere including oxygen for about 30 minutes.

In a second example of thermal processing, a thermal process can beperformed on the resultant structure at a temperature in the range ofabout 450° C. to 600° C. and in an inert gas atmosphere for about 30minutes. In a third example of thermal processing, a first thermalprocess can be performed on the resultant structure at a temperature inthe range of about 350° C. to 450° C. and in a gas atmosphere includingoxygen for about 30 minutes. Thereafter, a second thermal process can beperformed on the resultant structure at a temperature in the range ofabout 450° C. to 600° C. and in an inert gas atmosphere for about 30minutes.

In the first through third examples of thermal processing, the inert gasmay include, for example, argon Ar and/or nitrogen N₂, and the gasincluding oxygen may include oxygen gas O₂ and/or oxygen nitride gasNO₂. In the first and third examples of thermal processing, the firstand second thermal processes can be performed in situ. Accordingly, awafer does not need to be transferred between chambers so that defectson the wafer can be reduced.

It may be efficient to perform the thermal process in a gas atmosphereincluding oxygen. Oxygen, however, may permeate into the conductivelayer 130 for the upper electrode and the tantalum oxide layer 120 whenthe thermal process is performed at a temperature of over 600° C. and inthe gas atmosphere including oxygen. Thus, the thermal process may beperformed at a temperature of under 500° C. in an oxygen gas atmosphereand the thermal process may be performed at a temperature of over 500°C. in an inert gas atmosphere.

Because the thermal processes are collectively performed after theconductive layer for the upper electrode and the tantalum oxide layerhave been etched, interface stress between the conductive layer 130 forthe upper electrode and the tantalum oxide layer 120 may be efficientlyrelieved. In addition, because the heat can be transferred to thetantalum oxide layer 120 via exposed sidewalls of the tantalum oxidelayer 120, the tantalum oxide layer 120 may be cured. Furthermore, thethermal processes can be performed collectively to simplify the process.

Here, the dielectric constant and the leakage current of the tantalumoxide layer may be unaffected even if the thermal processes areperformed collectively after the etching process, as discussed belowwith reference to FIGS. 3 and 4. FIG. 3 is a graph illustrating anequivalent oxide thickness of the tantalum oxide layer according tofirst embodiments of the present invention discussed above with respectto FIGS. 2A-C. The first comparative example in the graph of FIG. 3refers to a capacitor manufactured as discussed above with respect toFIGS. 1A and 1B.

According to the graph, equivalent oxide thicknesses according to thefirst through third examples of thermal processing and an equivalentoxide thickness of the comparative example are similar. In other words,comparative thermal processes and collective thermal processes accordingto first embodiments of the present invention discussed above withrespect to FIGS. 2A-C can provide tantalum oxide layers having similardielectric constants.

FIG. 4 is a graph illustrating leakage currents of capacitors accordingto first through third examples of thermal processing according toembodiments of the present invention. According to the graph of FIG. 4,capacitor leakage currents according to the first through third examplesof thermal processing according to embodiments of the present inventionmay be lower than comparative capacitor leakage currents. In addition,the base-levels B of the leakage currents according to the first throughthird examples of thermal processes according to embodiments of thepresent invention may be lower than the base-level B of comparativeleakage currents. Furthermore, the take voltages Vt at which the leakagecurrents increase more dramatically may be more stable in capacitorsaccording to first through third examples of thermal processes accordingto embodiments of the present invention.

Based on the graphs of FIGS. 3 and 4, methods of performing thermalprocesses according to first through third examples of thermalprocessing according to embodiments of the present invention may providedielectric constants and/or equivalent oxide thicknesses, similar tothose of comparative methods. In addition, methods including the firstthrough third examples of thermal processing may significantly improveleakage currents. Methods of forming capacitors, according toembodiments of the present invention including first through thirdexamples of thermal processing, can provide tantalum oxide layers havingreduced thicknesses without significantly increasing leakage currents.Because dielectric layers formed according to first embodiments of thepresent invention discussed above with respect to FIGS. 2A-C can havedielectric constants similar to those of comparative dielectric layerswhile reducing leakage currents, thicknesses of dielectric layers can bereduced without significantly increasing leakage currents.

FIG. 5 is a graph illustrating leakage currents of capacitors withrespect to changes in temperature, according to the first embodiments ofthe present invention discussed above with respect to FIGS. 2A-C. Inparticular, capacitors of FIG. 5 are manufactured by methods includingthe second example of thermal processing according to embodiments of thepresent invention. According to the graph of FIG. 5, the leakagecurrents of the capacitor may not change significantly according tochanges in temperature, such as 25° C., 85° C., and 125° C. Accordingly,the leakage current of the dielectric layer may not be significantlydependent on the temperature. In addition, it may be assumed that thedielectric layer, i.e., the tantalum oxide layer, may be stably formed.

According to first embodiments of the present invention discussed abovewith respect to FIGS. 2A-C, by collectively performing the thermalprocessing after etching the upper electrode layer and the dielectriclayer, the process can be simplified and improved dielectric layers canbe obtained.

In addition, capacitor dielectric layers according to embodiments of thepresent invention discussed above with respect to FIGS. 2A-C can have adielectric constant similar to that of a comparative capacitordielectric layer while providing improved leakage currentcharacteristics. Accordingly, a stable capacitor can be formed and thecapacitance can be improved by reducing the thickness of the dielectriclayer, i.e., the tantalum oxide layer.

Processes according to second embodiments of the present invention canbe the same as those of first embodiments of the present invention withthe exception of temperatures used in the thermal processing of FIG. 2C.Methods according to second embodiments of the present invention willnow be described with FIGS. 2A through 2C.

Referring to FIG. 2C, a conductive layer 130 for an upper electrode anda tantalum oxide layer 120 can be dry etched. Thereafter, a thermalprocess can be performed to relieve interface stresses between theconductive layer 130 for the upper electrode and the tantalum oxidelayer 120, and to crystallize the tantalum oxide layer 120.

Here, the thermal process can be performed by various methods asdiscussed below. In a fourth example of thermal processing, a firstthermal process can be performed on the resultant structure at atemperature in the range of about 650 to 700° C. and in an inert gasatmosphere for about 30 minutes. Thereafter, a second thermal processcan be performed on the resultant structure at a temperature in therange of about 350° C. to 450° C. in a gas atmosphere including oxygenfor about 30 minutes. In a fifth example of thermal processing, athermal process can be performed on the resultant structure at atemperature in the range of about 650° C. to 700° C. and in an inert gasatmosphere and/or a gas atmosphere including nitrogen for about 30minutes.

In a sixth example of thermal processing, a first thermal process can beperformed on the resultant structure at a temperature in the range ofabout 350° C. to 450° C. and in a gas atmosphere including oxygen forabout 30 minutes. Thereafter, a second thermal process can be performedon the resultant structure at a temperature in the range of about 450°C. to 600° C. and in an inert gas atmosphere and/or a gas atmosphereincluding nitrogen for about 30 minutes. In the fourth and sixthexamples of thermal processing, the first and second thermal processescan be performed in situ. Accordingly, a wafer is not required to betransferred between chambers so that defects on the wafer can bereduced.

In the fourth through sixth examples of thermal processing, the inertgas may include Ar and/or N₂, and the gas including oxygen may includeO₂ and/or NO₂. The thermal processes can be performed after the etchingprocesses have been performed to efficiently relieve interface stressesbetween the conductive layer 130 for the upper electrode and thetantalum oxide layer 120. In addition, because heat can be transferredto the tantalum oxide layer 120 via exposed sidewalls of the tantalumoxide layer 120, the tantalum oxide layer 120 can be cured andcrystallized.

When the tantalum oxide layer 120 is crystallized at a temperature ofhigher than 650° C., the dielectric constant may be lowered and theleakage current may increase. A tantalum oxide layer in an amorphousstate may thus be used as the dielectric layer. However, when thethermal processes are collectively performed at a temperature greaterthan about 650° C. after dry etching has been performed, the dielectricconstant of the tantalum oxide layer may be similar to that of acrystalline tantalum oxide layer while significantly reducing leakagecurrents. It will now be described with reference to FIGS. 6 and 7.

FIG. 6 is a graph illustrating equivalent oxide thicknesses of tantalumoxide layers according to second embodiments of the present invention. Asecond comparative example in the graph of FIG. 6 refers to anequivalent oxide thickness of a tantalum oxide layer in a capacitormanufactured by depositing a tantalum oxide layer, performing a thermalprocess on the tantalum oxide layer at a temperature greater than 650°C., depositing an upper electrode, dry etching the upper electrode andthe tantalum oxide layer, and performing a thermal process to relieveinterface stresses between the upper electrode and the tantalum oxidelayer. According to the graph of FIG. 6, the equivalent oxidethicknesses according to the fourth through sixth examples of thermalprocessing, i.e., 10.5 Å, 10.5 Å, and 13.8 Å, are greater than thesecond comparative equivalent oxide thicknesses, i.e., about 9 Å, withthe differences being about 1 Å to 3 Å. In addition, the equivalentoxide thicknesses according to the fourth through sixth examples ofthermal processing are less than the thickness of the first comparativeequivalent oxide layer, i.e., about 14 Å. Therefore, tantalum oxidelayers according to methods including the fourth through sixth examplesof thermal processing may have dielectric constants similar to that ofcrystalline tantalum oxide layers and dielectric constants better thanthat of amorphous tantalum oxide layers.

On the other hand, FIG. 7 is a graph illustrating leakage currents ofcapacitors according to the fourth through sixth examples of thermalprocessing. According to the graph of FIG. 7, leakage currents of thecapacitors according to the fourth through sixth examples of thermalprocessing may be lower than leakage currents of the second comparativecapacitor. In addition, base-levels B of the leakage currents accordingto the fourth through sixth examples of thermal processing may be lowerthan the base-level B of second comparative leakage currents.Furthermore, take voltages Vt at which the leakage currents are increasesignificantly may be improved in the fourth through sixth examples ofthermal processing. As a result, even when the tantalum oxide layer 120is crystallized as shown in second embodiments of the present invention,leakage currents can be stable and dielectric constants can be improved.

FIGS. 8A through 8C are cross-sectional views illustrating methods formanufacturing semiconductor memory devices according to thirdembodiments of the present invention. Referring to FIG. 8A, a conductivelayer 210 for a lower electrode is deposited on a semiconductorsubstrate 200. The conductive layer 210 for the lower electrode may beformed of, for example, a metal such as Pt, Ru, Ir, Rh, and/or Os havinga relatively high work function. A tantalum oxide layer seed layer 220can be deposited on the conductive layer 210 for the lower electrode toa thickness, for example, in the range of about 30 to 60 Å. Thereafter,the seed layer 220 can be crystallized at a temperature in the range ofabout 650° C. to 750° C. Because the seed layer 220 can be a relativelythin layer, the thermal process on the seed layer 220 can be performedfor a relatively short time.

Referring to FIG. 8B, a tantalum oxide layer 230 can be deposited on theseed layer 220. Here, the tantalum oxide layer 230 can be formed usingchemical vapor deposition (CVD) at a temperature in the range of about380° C. to 500° C. Because the tantalum oxide layer 230 can be depositedon the crystalline seed layer 220, a portion of the tantalum oxide layer230 can be crystallized. Thereafter, a conductive layer 240 for an upperelectrode can be deposited on the tantalum oxide layer 230. Theconductive layer 240 for the upper electrode can be formed of the samematerial as the conductive layer 210 for the lower electrode. Curingused to improve dielectric characteristics of the tantalum oxide layer230 can be omitted between depositing the tantalum oxide layer 230 anddepositing the conductive layer 240 for the upper electrode.

Referring to FIG. 8C, the conductive layer 240 for the upper electrode,the tantalum oxide layer 230, and the seed layer 220 can be dry etchedto expose portions of the conductive layer 210 for the lower electrode.Accordingly, the sidewalls of the conductive layer 240 for the upperelectrode, the tantalum oxide layer 230, and the seed layer 220 can beexposed. Next, a thermal process can be performed on the resultantstructure to relieve interface stresses between the conductive layer 240for an upper electrode and the tantalum oxide layer 230 and to improvedielectric characteristics of the tantalum oxide layer 230. In thepresent embodiments, a first thermal process can be performed on theresultant structure at a temperature in the range of about 450° C. to600° C. and in an inert gas atmosphere for about 30 minutes. Thereafter,a second thermal process can be performed on the resultant structure ata temperature in the range of about 350° C. to 450° C. in a gasatmosphere including oxygen for about 30 minutes. In this case, theinert gas may include Ar and/or N₂, and the gas including oxygen mayinclude O₂ and/or NO₂. In third embodiments, the first and secondthermal processes can be performed in situ. Accordingly, when thetantalum oxide layer 230 is formed using the seed layer 220 and thethermal processes are collectively performed after the dry etchingprocess, stable dielectric constants and reduced leakage currents can beobtained.

FIG. 9 is a graph illustrating equivalent oxide thicknesses of thetantalum oxide layer according to third embodiments of the presentinvention. A third comparative example in the graph of FIG. 9 refers tothe thickness of a tantalum oxide layer in a capacitor, manufactured byforming a seed layer, crystallizing the seed layer, depositing atantalum oxide layer, curing the tantalum oxide layer, depositing anupper electrode, dry etching the upper electrode and the tantalum oxidelayer, and performing a thermal process to relieve interface stressesbetween the upper electrode and the tantalum oxide layer. The equivalentoxide thickness according to third embodiments of the present inventionis similar to that of the third comparative equivalent oxide thicknessso that the dielectric constants are similar.

FIG. 10 is a graph illustrating leakage currents of a capacitoraccording to third embodiments of the present invention. Referring tothe graph of FIG. 10, leakage currents of the capacitor according tothird embodiments of the present invention may be less than that of thethird comparative capacitor.

Accordingly, methods according to third embodiments of the presentinvention may omit curing of the tantalum oxide layer to reducetransferring of a wafer between chambers and to reduce an amount of timefor processes. In addition, methods according to third embodiments ofthe present invention may reduce leakage currents to provide a stablecapacitor and to realize a high capacitance.

As described above, a thermal process for curing the dielectric layermay be omitted after the dielectric layer is deposited. Thermalprocesses for relieving interface stresses between the upper electrodeand the dielectric layer and the curing process of the dielectric layermay be collectively performed after the upper electrode and thedielectric layer are dry etched. Thus, the number of thermal processescan be reduced so that wafer transfers and process times can be reduced.

In addition, the tantalum oxide layers formed by methods according toembodiments of the present invention may have dielectric constantssimilar to those of comparative tantalum oxide layers and may haveimproved leakage current characteristics. Accordingly, a stablecapacitor can be formed and the thickness of the dielectric layer, i.e.the tantalum oxide layer, can be reduced to provide a relatively highcapacitance.

Embodiments of the present invention may provide simplified methods formanufacturing semiconductor memory devices. According to embodiments ofthe present invention, methods may be provided for fabricating asemiconductor memory device. After depositing a conductive layer for alower electrode on a semiconductor substrate, a dielectric layer can bedeposited on the conductive layer for the lower electrode, and aconductive layer for an upper electrode can be deposited on thedielectric layer. Thereafter, portions of the conductive layer for theupper electrode and the dielectric layer can be etched, and a thermalprocess can be performed on the conductive layer for the upper electrodeand the dielectric layer.

According to additional embodiments of the present invention, methodscan be provided for fabricating semiconductor memory devices. Afterdepositing a conductive layer for a lower electrode on a semiconductorsubstrate, a tantalum oxide layer can be deposited on the conductivelayer for the lower electrode, and a conductive layer for an upperelectrode can be deposited on the tantalum oxide layer. Thereafter,portions of the conductive layer for the upper electrode and thetantalum oxide layer can be dry etched. A thermal process can beperformed to reduce an interface stress between the conductive layer forthe upper electrode and the tantalum oxide layer and to cure thetantalum oxide layer. Here, the tantalum oxide layer may maintain asubstantially amorphous state after the thermal process.

The thermal process may include performing a first thermal process onthe resultant structure at a temperature in the range of about 450° C.to 600° C. in an inert gas atmosphere, and performing a second thermalprocess on the semiconductor resultant structure at a temperature in therange of about 350° C. to 450° C. in a gas atmosphere including oxygen.The thermal process may be performed on the resultant structure at atemperature in the range of about 450° C. to 600° C. in an inert gasatmosphere. The thermal process may alternately include performing afirst thermal process on the resultant structure at a temperature in therange of about 350° C. to 450° C. in a gas atmosphere including oxygen,and performing a second thermal process on the resultant structure at atemperature in the range of about 450° C. to 600° C. in an inert gasatmosphere.

According to still additional embodiments of the present invention,methods may be provided for fabricating semiconductor memory devices.After depositing a conductive layer for a lower electrode on asemiconductor substrate, a tantalum oxide layer can be deposited on theconductive layer for the lower electrode, and a conductive layer for anupper electrode can be deposited on the tantalum oxide layer.Thereafter, portions of the conductive layer for the upper electrode andthe tantalum oxide layer can be dry etched. A thermal process can beperformed to reduce an interface stress between the conductive layer forthe upper electrode and the tantalum oxide layer, and to crystallize atleast a portion of the tantalum oxide layer.

Here, the thermal process may include performing a first thermal processon the resultant structure at a temperature in the range of about 650°C. to 700° C. in an inert gas atmosphere, and performing a secondthermal process on the semiconductor resultant structure at atemperature in the range of about 350° C. to 450° C. in a gas atmosphereincluding oxygen. The thermal process may be performed on the resultantstructure at a temperature in the range of about 650° C. to 700° C. inan inert gas atmosphere. The thermal process may alternately includeperforming a first thermal process on the resultant structure at atemperature in the range of about 350° C. to 450° C. in a gas atmosphereincluding oxygen, and performing a second thermal process on theresultant structure at a temperature in the range of about 650° C. to700° C. in an inert gas atmosphere.

According to yet additional embodiments of the present invention,methods may be provided for fabricating semiconductor memory devices.After depositing a conductive layer for a lower electrode on asemiconductor substrate, a seed layer of a tantalum oxide layer can bedeposited on the conductive layer for the lower electrode, and thetantalum oxide layer seed layer can be crystallized. Thereafter, atantalum oxide layer can be deposited on the crystallized tantalum oxideseed layer, and a conductive layer for an upper electrode can bedeposited on the tantalum oxide layer. Portions of the conductive layerfor the upper electrode and the tantalum oxide layer can be dry etched.Next, a thermal process can be performed to reduce an interface stressbetween the conductive layer for the upper electrode and the tantalumoxide layer, and to cure the tantalum oxide layer.

Here, the thermal process may include performing a first thermal processon the resultant structure at a temperature in the range of about 450°C. to 600° C. in an inert gas atmosphere, and performing a secondthermal process on the resultant structure at a temperature in the rangeof about 350° C. to 450° C. in a gas atmosphere including oxygen. Thefirst and second thermal processes can be performed in situ. The inertgas may include argon Ar or nitrogen N₂, and the gas including oxygenmay include oxygen gas O₂ or oxygen nitride gas NO₂.

The tantalum oxide seed layer may be formed to a thickness in the rangeof about 30 Å to 60 Å, and the tantalum oxide seed layer may becrystallized by performing a thermal process at a temperature in therange of about 650° C. to 750° C. The conductive layer for a lowerelectrode can be formed of at least one material selected from the groupof platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh), and/orosmium (Os), and the conductive layer for an upper electrode can beformed of the same material as the conductive layer for the lowerelectrode. In addition, the tantalum oxide layer may be deposited at atemperature in the range of about 380° C. to 500° C. using chemicalvapor deposition (CVD).

While this invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A method for fabricating a semiconductor device, the methodcomprising: forming a first conductive layer for a first electrode on asemiconductor substrate; forming a dielectric layer on the firstconductive layer; forming a second conductive layer for a secondelectrode on the dielectric layer; removing portions of the secondconductive layer and the dielectric layer; and performing a thermalprocess on the second conductive layer and the dielectric layer at atemperature of at least about 400° C., wherein the thermal processcomprises, heating the second conductive layer and the dielectric layerto a first temperature in the range of about 450° C. to 600° C. in aninert gas atmosphere, and then, heating the second conductive layer andthe dielectric layer to a second temperature in the range of about 350°C. to 450° C. in a gas atmosphere including oxygen.
 2. The method ofclaim 1, wherein forming the dielectric layer is preceded by: depositinga seed layer on the first conductive layer; and crystallizing the seedlayer.
 3. The method of claim 1, wherein the performing the thermalprocess comprises heating the dielectric layer and the second conductivelayer at a temperature in the range of about 450° C. to 600° C. in aninert gas atmosphere.
 4. A method for fabricating a semiconductordevice, the method comprising: forming a first conductive layer for afirst electrode on a semiconductor substrate; forming a dielectric layeron the first conductive layer; forming a second conductive layer for asecond electrode on the dielectric layer; removing portions of thesecond conductive layer and the dielectric layer; and performing athermal process on the second conductive layer and the dielectric layerat a temperature of at least about 400° C., wherein performing thethermal process comprises, heating the dielectric layer and the secondconductive layer at a first temperature in the range of about 650° C. to700° C. in an inert gas atmosphere, and then, heating the dielectriclayer and the second conductive layer at a second temperature in therange of about 350° C. to 450° C. in a gas atmosphere including oxygen.5. A method for fabricating a semiconductor device, the methodcomprising: forming a first conductive layer for a first electrode on asemiconductor substrate; forming a dielectric layer on the firstconductive layer; forming a second conductive layer for a secondelectrode on the dielectric layer; removing portions of the secondconductive layer and the dielectric layer; and performing a thermalprocess on the second conductive layer and the dielectric layer at atemperature of at least about 400° C., wherein performing the thermalprocess comprises heating the dielectric layer and the second conductivelayer at a temperature in the range of about 650° C. to 700° C. in aninert gas atmosphere.
 6. The method of claim 1, wherein the firstconductive layer comprises at least one material selected from the groupconsisting of platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh),and/or osmium (Os).
 7. The method of claim 6, wherein the secondconductive layer comprises a same material as the first conductivelayer.
 8. The method of claim 1, wherein forming the dielectric layercomprises forming a tantalum oxide layer.
 9. The method of claim 1,wherein forming the dielectric layer comprises depositing tantalum oxideat a temperature in the range of about 380° C. to 500° C. using chemicalvapor deposition (CVD).
 10. The method of claim 1, wherein removingportions of the second conductive layer and the dielectric layercomprises dry etching the second conductive layer and the dielectriclayer.
 11. The method of claim 1 wherein performing the thermal processcomprises performing the thermal process on the second conductive layerand the dielectric layer after removing portions of the secondconductive layer and the dielectric layer.
 12. A method for fabricatinga semiconductor device, the method comprising: forming a firstconductive layer for a first electrode on a semiconductor substrate;forming a tantalum oxide layer on the first conductive layer; forming asecond conductive layer for a second electrode on the tantalum oxidelayer; removing portions of the second conductive layer and the tantalumoxide layer; and performing a thermal process to reduce an interfacestress between the second conductive layer and the tantalum oxide layerand to cure the tantalum oxide layer, while maintaining the tantalumoxide layer in a substantially amorphous state during and after thethermal process, wherein performing the thermal process comprises,heating the tantalum oxide layer and the second conductive layer at afirst temperature in the range of about 450° C. to 600° C. in an inertgas atmosphere, and then, heating the tantalum oxide layer and thesecond conductive layer at a second temperature in the range of about350° C. to 450° C. in a gas atmosphere including oxygen.
 13. The methodof claim 12, wherein heating at the first temperature and heating at thesecond temperature are performed in situ.
 14. The method of claim 12,wherein performing the thermal process comprises heating the tantalumoxide layer and the second conductive layer at a temperature in therange of about 450° C. to 600° C. in an inert gas atmosphere.
 15. Amethod for fabricating a semiconductor device, the method comprising:forming a first conductive layer for a first electrode on asemiconductor substrate; forming a tantalum oxide layer on the firstconductive layer; forming a second conductive layer for a secondelectrode on the tantalum oxide layer; removing portions of the secondconductive layer and the tantalum oxide layer; and performing a thermalprocess to reduce an interface stress between the second conductivelayer and the tantalum oxide layer and to cure the tantalum oxide layer,while maintaining the tantalum oxide layer in a substantially amorphousstate during and after the thermal process, wherein the thermal processis performed in situ.
 16. The method of claim 12, wherein the firstconductive layer comprises at least one material selected from the groupconsisting of Pt, Ru, Ir, Rh, and/or Os.
 17. The method of claim 16,wherein the second conductive layer comprises a same material as thefirst conductive layer.
 18. The method of claim 12, wherein forming thetantalum oxide layer comprises depositing tantalum oxide at atemperature in the range of about 380° C. to 500° C. using chemicalvapor deposition.
 19. A method for fabricating a semiconductor device,the method comprising: forming a first conductive layer for a firstelectrode on a semiconductor substrate; forming a tantalum oxide layeron the first conductive layer; forming a second conductive layer for asecond electrode on the tantalum oxide layer; removing portions of thesecond conductive layer and the tantalum oxide layer; and performing athermal process to reduce interface stress between the second conductivelayer and the tantalum oxide layer and to crystallize at least a portionof the tantalum oxide layer.
 20. The method of claim 19, whereinperforming the thermal process comprises: heating the second conductivelayer and the tantalum oxide layer at a second temperature in the rangeof about 650° C. to 700° C. in an inert gas atmosphere; and then,heating the second conductive layer and the tantalum oxide layer at asecond temperature in the range of about 350° C. to 450° C. in a gasatmosphere including oxygen.
 21. The method of claim 20, wherein heatingat the first temperature and heating at the second temperature areperformed in situ.
 22. The method of claim 19, wherein performing thethermal process comprises heating the second conductive layer and thetantalum oxide layer at a temperature in the range of about 650° C. to700° C. in an inert gas atmosphere.
 23. The method of claim 19, whereinperforming the thermal process comprises: heating the second conductivelayer and the tantalum oxide layer at a first temperature in the rangeof about 350° C. to 450° C. in a gas atmosphere including oxygen; andthen, heating the second conductive layer and the tantalum oxide layerat a second temperature in the range of about 650° C. to 700° C. in aninert gas atmosphere.
 24. The method of claim 23, wherein heating at thefirst temperature and heating at the second temperature are performed insi/it.
 25. The method of claim 19, wherein the first conductive layercomprises at least one material selected from the group consisting ofPt, Ru, Ir, Rh, and/or Os.
 26. The method of claim 25, wherein thesecond conductive layer comprises a same material as the firstconductive layer.
 27. The method of claim 19, wherein forming thetantalum oxide layer comprises depositing tantalum oxide at atemperature in the range of 380° C. to 500° C. by a CVD method.
 28. Themethod of claim 1 wherein forming a second conductive layer for a secondelectrode on the dielectric layer comprises forming a second conductivelayer for a second electrode on the dielectric layer without performinga Thermal process to cure the dielectric layer between depositing thedielectric layer and forming the second conductive layer.
 29. The methodof claim 4 wherein forming a second conductive layer for a secondelectrode on the dielectric layer comprises forming a second conductivelayer for a second electrode on the dielectric layer without performinga thermal process to cure the dielectric layer between depositing thedielectric layer and forming the second conductive layer.
 30. The methodof claim 5 wherein forming a second conductive layer for a secondelectrode on the dielectric layer comprises forming a second conductivelayer for a second electrode on the dielectric layer without performinga thermal process to cure the dielectric layer between depositing thedielectric layer and forming the second conductive layer.
 31. The methodof claim 12 wherein forming a second conductive layer for a secondelectrode on the dielectric layer comprises forming a second conductivelayer for a second electrode on the dielectric layer without performinga thermal process to cure the dielectric layer between depositing thedielectric layer and forming the second conductive layer.
 32. The methodof claim 1 wherein performing the thermal process comprises performingthe thermal process after removing portions of the second conductivelayer and the dielectric layer.
 33. The method according to claim 32wherein removing portions of the second conductive layer and thedielectric layer comprises removing portions of the second conductivelayer and the dielectric layer from first portions of the firstconductive layer and maintaining portions of the dielectric layer onsecond portions of the first conductive layer, and wherein performingthe thermal process comprises performing the thermal process whilemaintaining the first portions of the first conductive layer.
 34. Themethod of claim 4 wherein performing the thermal process comprisesperforming the thermal process after removing portions of the secondconductive layer and the dielectric layer.
 35. The method according toclaim 34 wherein removing portions of the second conductive layer andthe dielectric layer comprises removing portions of the secondconductive layer and the dielectric layer from first portions of thefirst conductive layer and maintaining portions of the second conductivelayer and the dielectric layer on second portions of the firstconductive layer, and wherein performing the thermal process comprisesperforming the thermal process while maintaining the first portions ofthe first conductive layer.
 36. The method of claim 5 wherein performingthe thermal process comprises performing the thermal process afterremoving portions of the second conductive layer and the dielectriclayer.
 37. The of to claim 36 wherein removing portions of the secondconductive layer and the dielectric layer comprises removing portions ofthe second conductive layer and the dielectric layer from first portionsof the first conductive layer and maintaining portions of the secondconductive layer and the dielectric layer on second portions of thefirst conductive layer, and wherein performing the thermal processcomprises performing the thermal process while maintaining the firstportions of the first conductive layer.
 38. The method of claim 12wherein performing the thermal process comprises performing the thermalprocess after removing portions of the second conductive layer and thetantalum oxide layer.
 39. The of to claim 38 wherein removing portionsof the second conductive layer and the tantalum oxide layer comprisesremoving portions of the second conductive layer and the tantalum oxidelayer from first portions of the first conductive layer and maintainingportions of the second conductive layer and the tantalum oxide layer onsecond portions of the first conductive layer, and wherein performingthe thermal process comprises performing the thermal process whilemaintaining the first portions of the first conductive layer.
 40. Themethod of claim 15 wherein performing the thermal process comprisesperforming the thermal process after removing portions of the secondconductive layer and the tantalum oxide layer.
 41. The method of claim40 wherein removing portions of the second conductive layer and thetantalum oxide layer comprises removing portions of the secondconductive layer and the tantalum oxide layer from first portions of thefirst conductive layer and maintaining portions of the second conductivelayer and the tantalum oxide layer on second portions of the firstconductive layer, and wherein performing the thermal process comprisesperforming the thermal process while maintaining the first portions ofThe first conductive layer.
 42. The method of claim 19 whereinperforming the thermal process comprises performing the thermal processafter removing portions of The second conductive layer and the tantalumoxide layer.
 43. The method of claim 42 wherein removing portions of thesecond conductive layer and the tantalum oxide layer comprises removingportions of the second conductive layer and the tantalum oxide layerfrom first portions of the first conductive layer and maintainingportions of the second conductive layer and the tantalum oxide layer onsecond portions of the first conductive layer, and wherein performingthe thermal process comprises performing the thermal process whilemaintaining the first portions of the first conductive layer.
 44. Amethod according to claim 1 wherein the inert gas atmosphere comprisesan inert gas atmosphere without oxygen.
 45. A method according to claim4 wherein the inert gas atmosphere comprises an inert gas atmospherewithout oxygen.
 46. A method according to claim 5 wherein the inert gasatmosphere comprises an inert gas atmosphere without oxygen.
 47. Amethod according to claim 12 wherein the inert gas atmosphere comprisesan inert gas atmosphere without oxygen.
 48. A method according to claim20 wherein the inert gas atmosphere comprises an inert gas atmospherewithout oxygen.
 49. A method according to claim 23 wherein the inert gasatmosphere comprises an inert gas atmosphere without oxygen.